Such devices are generally known in game machines provided with a grabber or a vacuum head. A game machine provided with a grab crane is described, for example, in European Published Patent Application No. 1 233 824, which describes the use of an infrared sensor or switch for detecting the presence of a prize in the grabber claws. This is only a purely theoretical possibility, however, which is not very feasible in practice. Because of the available mounting possibilities and the spatial limitations, an infrared sensor is very difficult to incorporate in a normally functioning grabber.
U.S. Pat. No. 5,855,374 describes a game machine of the kind described in the introduction fitted with a vacuum head. This device is provided with a vacuum sensor for detecting the presence of a prize in the vacuum head.